Question: Since what time Bern has the head of government as Alexander Tschäppät?
Paraphrase: When did Alexander Tschappat begin his role as the head of government of Bern?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q70 p:P6 ?s . ?s ps:P6 wd:Q74144 . ?s pq:P580 ?value}